They charge a fee for holding the item and loaning money on it.
If you go in with something of value, they estimate what they can get for it they have to sell it and offer you some part of that. Say the retail is $200, but they think they could only get $100, they might offer $80-90. If you take it, you leave your item and take the money and a ticket. If you find you can redeem the item, you take in the cash you got, plus an additional amount which is the equivalent of interest and you get your item back. [I have not actually done this - the more likely way to collect the fee may be to deduct it from the amount given out. "I can give you $90 on that" actually means you walk out with $85 and have to come in with $90 to get the item back.]
Some (or all where law allows) will keep the item (not sell it) if you will come in with the "interest"/fee to pay for more holding time.
they buy items for less from customers
they sell the items for much more
therefore they make a profit